Monoclonal antibodies (mAbs) represent an important and rapidly growing class of therapeutics to treat cancer and other diseases, and their success has lead to extensive re-engineering efforts to improve and extend their functionality. Recently, we have uncovered a completely novel and highly specific interaction between a therapeutic antibody and a small peptide (a meditope). We hypothesize that this interaction can be exploited to more effectively target diseased tissue, potentially reduce adverse side effects, and lower the cost compared to current treatments involving combination of monoclonal antibodies. Towards these goals, we have demonstrated that we can couple this meditope to an antigen binding scaffold and target cells overexpressing the tumor antigen EGFR that have been pre-treated with the therapeutic monoclonal antibody against EGFR (cetuximab). This application leverages a new super-resolution protocol we recently developed which allows for quantitative investigation of single-molecule distribution on the plasma membrane. We will use super-resolution microscopy to systematically optimize multivalent meditopes as leads for cancer therapy and imaging. This combination of unique reagents and single molecule detection is highly innovative, and its successful demonstration will set the stage to develop and optimize new multivalent ligands to treat multiple cancer types.